telnet, rlogin, ssh, IP's and ports (was: Java Error)

[Lindy Mayfield]

(Funny how I so often get port 23 mixed up with 25, but never 25 confused with 
23.  A strange form of lysdexia I think.)  

Anyway I think it will take me some time to fully understand all you've 
written.  

But one question to clarify.  Are you saying that I can setup the telnet port 
(usually 23) to be a TSO connection and the rlogin port (usually 513) to 
connect to rlogind -- which seems to me to be the most usual setup -- OR I can 
use one port, say telnet 23, and take advantage of VIPA's such that I get to 
either TSO or rlogind via a (virtual) IP address?

So in one case I change the port number, and in the other case I change the IP 
address?

-Lindy


-Original Message-
From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of 
Chris Mason
Sent: Sunday, November 05, 2006 6:15 AM
To: IBM-MAIN@BAMA.UA.EDU
Subject: Re: Java Error

Chris said:

Now we can be thankful for VIPAs which have the property not to tie an IP 
address to an interface but to tie an IP address to an IP node or, even better 
as in fact here, to tie an IP address to a particular application on an IP 
node. In fact, using VIPAs we no longer need a port number in order to locate a 
"server" application. This, however, is not possible because the underlying IP 
demultiplexing logic insists on processing a port number.

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Re: telnet, rlogin, ssh, IP's and ports (was: Java Error)

[Chris Mason]

I'm sorry this is not properly "tied" to previous posts.

Lindy, Matt, Mark and Ramiro

Something that may be relevant to this topic for two reasons. It is certainly 
relevant for one reason.

In looking up the manuals for another problem, I discovered that there were two 
flavours of the "remote execution server", one which accesses TSO and another 
which access "UNIX" or some may say "USS", meaning "UNIX System Services". This 
"rang a bell" when I remembered your post with the sentence:



Correct me, please, if I am wrong, but if you telnet to port 25 you get to TSO, 
but if you rlogin to port 513 you get to USS.



In fact there are two flavours of two "remote execution servers". They happen 
to use ports either side of the RLOGIN port, namely 512 for REXEC, "exec" and 
514 for RSH, "shell".

These may be useful for the task to be performed that gave rise to this thread.

What is definitely relevant is the matter of running a service in either 
environment, TSO or UNIX (USS) and it is described in section 2.19.5, 
"Configuring TSO and z/OS UNIX Remote Execution servers to use the same port" 
of z/OS V1R8.0 Communications Server IP Configuration Guide. The technique I 
was describing in an earlier post is covered yet again but "officially", as it 
were, being in a regular manual and in some detail including how to define a 
VIPA and an example of a NETSTAT command.

I would differ from the example here only in defining two VIPAs not just the 
one, one for each environment, TSO and UNIX (USS).

Note also the need to use INETD - also for otelnetd - which is covered in 
section APPENDIX1.1, "Appendix A. Setting up the inetd configuration file" of 
z/OS V1R8.0 Communications Server IP Configuration Guide.

Chris Mason

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